In the orthopedic surgery of bone, discontinuities such as drilled holes and interfaces between bone and a prosthetic device, are important because they result in a concentration of stress which can lead to fracture of the bone. Traditional elasticity theory, which has been successful in predicting the behavior of engineering materials, does not correctly predict the stress-concentration in bone. Couple-stress or asymmetric elasticity theory is a generalization of traditional elasticity, which admits an internal twisting force per unit area, as well as the usual force per unit area or stress. This theory predicts stress-concentrations which differ from those predicted by the traditional theory. Theoretical considerations suggest that structured materials such as bone, are likely to exhibit marked couple-stress elasticity. A review of the experimental literature on bone reveals results which are inconsistent with traditional elasticity and with viscoelasticity theory, but which are consistent with couple-stress theory. It is therefore hypothesized that bone does in fact exhibit couple-stress elasticity and it is proposed that experiments be performed to these this hypothesis. Methods to be used include the measurement of the effect of specimen size on the apparent stiffness of bone specimens in quasistatic torsion and bending. Theory predicts that the results of such experiments will disclose the presence of couple-stress and the magnitude of the couple-stress elastic coefficients. Several benefits which might result from the proposed study are: (1) Accurate prediction of stress concentration around holes drilled in bone during surgery, and around holes containing bone pins or screws, in various geometries. (2) Development of an extended constitutive model which will permit more accurate solution of problems in the stress analysis of bone and bone-implant systems.